Helium and mixtures thereof with carbon dioxide as fire extinguishants



Patented June 9, 1953 CARBON DIOXIDE as FIRE EXTINGUISHANTS 1 4 Richard L. Tuve, silver 'sfiriiigjivid' No Drawing. Application March 10, 1948, Serial No. 14,141

6 Claims. (01. 169-1) (Granted under Title 35, U. S. Code (1952),

sec. 266) 1 This invention relates to the use of an inert gas as a fire extinguishant. In particular it relates to the use of helium gas, alone and in admixture with other non-combustion supporting gases for this purpose.

The mechanism of extinguishing fires by the use of non-combustion supporting gases con-,

sists in excluding air (oxygen) from the atmosphere enveloping the burning material. Carbon dioxide gas is the standard substance employed for this purpose and its use is very common.

The general object of this invention is to pro vide a non-combustion supporting gas for use in extinguishing fires.

A further object is to provide such a gas having a high difiusion rate.

In particular it is the object of this invention to provide a gas for extinguishing fires (e. g. starting by spontaneous combustion) in the interior of tightly packed combustibles such as bales of cotton, grain stored in elevators, etc.

Fires of this nature are extremely difficult to extinguish by use of carbon dioxide, due to the high molecular weight of the gas and its consequent low diifusion rate. A fire starting in the upper region of a grain elevator, e. g. can be extinguished by carbon dioxide only by introducing the gas at or near the level of the fire. The mechanical difficulties raised by such a restriction are obvious. If helium gas is employed it may be introduced at the bottom of the elevator and will rapidly rise to the region of the fire and extinguish it.

Even a heavy gas is inefiective if introduced from above a fire, as would be the logical way of introducing extinguishant into, for example, a material burning in the hold of a ship. The hot gases rising from the combustion region simply carry away the extinguishant. Thus, in these applications also, a light, highly diffusible gas which will quickly rise from below the burning region could be used with great advantage.

In comparing the eificiency of helium with carbon dioxide as a fire extinguishant it is necessary to point out that about 1.7 times as much helium by volume is required to extinguish combustion. However, this disadvantage is more than offset by the fact that helium diffuses about 3.3 times as fast as carbon dioxide. Thus, theoretically, helium should extinguish a fire.

or 1.9 times as fast as CO2.

Mixtures of helium and carbon dioxide are 2 also efiicient fire extinguishing agents. A. gaseous mixture of 50% C02 and 50% He has the advantages of a relatively high difiustion rate and of a lesser volume than of helium alone being required to extinguish a fire.

In a series of tests where the respective gases were required to difiuse through a membrane to a combustion chamber, it was found that an average of 2 minutes 42 seconds were required for carbon dioxide to extinguish the fiame, while only 1 minute 38 seconds were required for helium. Thus, experimentally, helium extinguishes a fire 1.62 sec.

.98 sec.

or 1.6 times as fast as carbon dioxide.

The invention described herein may be made and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. The method of extinguishing a fire in tightly packed combustible material comprising introducing helium gas thereto and permitting the same to difiuse through the material and extinguish the fire.

2. The method of extinguishing a fire in tightly packed combustible material lying within a confined space comprising introducing helium gas into the confined space below the fire to rise and diffuse into the region of the fire and extinguish the same.

3. The method of extinguishing a fire situated behind gas-permeable material and within a combined space comprising introducing helium gas to the material and permitting it to diffuse rapidly through the material and extinguish the fire.

4. A fire extinguishing composition comprising essentially an admixture of substantial proportions of carbon dioxide and helium, the amount of the helium being sufficient to give the composition a high rate of clifiusion relative to that of carbon dioxide alone.

5. A fire extinguishing composition characterized by relatively high rate of diffusion consisting of 50% helium and 50% carbon dioxide.

6. The method of extinguishing a fire in combustible material located within a confined space which comprises introducing to the material for diffusion therethrough, a gas mixture comprising essentially substantial proportions of carbon dioxide and helium, the amount of the he- Hum being sumclent to give the gas mixture a high rate of difiusion relative to that of carbon dioxide alone.

V RICHARD L. TUVE.

References Cited in the file of this patent UNITED STATES PATENTS Davidson 5,1911

Number Name fiate 1,641,814 Jones Sept. 6, 1927 1,703,408 Smith Feb. 26, 1929 2,143,311 .Geertz Jan. 10, 1939 2,260,515 Ensminger et a1. Oct. 28, 1941 2,409,388 Rees Q. Oct. 15, 1946 OTHER REFERENCES Mellors Modern Inorg. Chem., Revised Ed. (1939), Longmans, Green & 00., N. Y., pages 541 (and 542. 

1. THE METHOD OF EXTINGUISHING A FIRE IN TIGHTLY PACKED COMBUSTIBLE MATERIAL COMPRISING INTRODUCING HELIUM GAS THERETO AND PERMITTING THE SAME TO DIFFUSE THROUGH THE MATERIAL AND EXTINGUISH THE FIRE. 